[wip]provider: provider_meta support with structural attributes

[jar-b]

Description

This PR will not be merged. It is only intended to record the attempted implementation of provider_meta with structural attributes, and document why this approach does not work within the current constraints of the AWS provider.

Background

The AWSCC provider already has a working implementation of provider_meta support in which the schema contains a single user_agent attribute that is a list of objects. This schema matches the existing provider-level configuration attribute of the same name. Notably, the AWSCC provider uses only Terraform Plugin Framework and operates with Terraform Protocol V6.

  provider_meta "awscc" {
    user_agent = [
      {
        product_name    = "jb-demo"
        product_version = "0.0.1"
        comment         = "a demo module"
      },
    ]
  }

In an ideal scenario, the standard provider would match the rough shape of the schema, but replace list attributes with blocks.

  provider_meta "aws" {
    user_agent {
      product_name    = "jb-demo"
      product_version = "0.0.1"
      comment         = "a demo module"
    }
  }

However, the schema cannot be written in this way as Terraform Protocol V5 doesn't support structural attributes, meaning an attribute with this shape can't be defined in the protocol at all.

│ Error: Failed to load plugin schemas
│
│ Error while loading schemas for plugin components: Failed to obtain provider schema: Could not load the schema for provider registry.terraform.io/hashicorp/aws: failed to retrieve
│ schema from provider "registry.terraform.io/hashicorp/aws": Error converting provider_meta schema: The provider_meta schema couldn't be converted into a usable type. This is always
│ a problem with the provider. Please report the following to the provider developer:
│
│ AttributeName("user_agent"): protocol version 5 cannot have Attributes set..

Additionally, even if the provider were upgraded to Terraform Protocol V6, Terraform Plugin Framework lacks support for blocks in the metaschema.Schema struct, making it impossible to match the schema shape between the Plugin SDK V2 and Plugin Framework providers as required by terraform-plugin-mux.¹

Footnotes

1. This particular limitation means that the standard provider will effectively never be able to implement a structural attribute in provider_meta. Eliminating muxing from the provider would require thousands of Plugin SDK V2 based resources to be migrated to Plugin Framework. There is no currently available tooling which makes this feasible at the scale of the AWS provider. ↩

[github-actions]

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[github-actions]

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